Loud sounds produce a startle responses that arise in the auditory system. Loud sounds are directionally detected to one side or the other. Muscles tense and the head turns to the side of the loudest sound.

Loud sounds produce a startle responses that arise in the auditory system. Loud sounds are directionally detected to one side or the other. Muscles tense and the head turns to the side of the loudest sound.
The auditory pathway incoming via the eighth nerve enters at the pons-medulla junction and ascends on the same side and through the trapezoid body and up the lateral lemniscus to the inferior colliculus. This pathway is crossed and uncrossed in the trapezoid body.
The inferior colliculus forms the descending tectospinal projection to the ambiguus nucleus innervating the 11th nerve for turning the head. Dorsal to the medial lemniscus, the tectospinal tract projects to the cord through the ventral funiculus of the cord to connect with interneurons that target neck motor neurons as well as motor neuons tensing the trunk muscules.

The auditory pathway incoming via the eighth nerve enters at the pons-medulla junction and ascends on the same side and through the trapezoid body and up the lateral lemniscus to the inferior colliculus. This pathway is crossed and uncrossed in the trapezoid body.